1. Field of the Invention
This invention relates generally to piston rings for internal combustion engines, materials thereof, and methods of forming the same.
2. Description of the Prior Art
Piston rings of internal combustion engine applications are often formed of cast iron compositions providing wear resistance and seizure resistance. U.S. Pat. No. 5,972,128 to Miwa discloses cast iron compositions used to form piston rings. The cast irons disclosed in Miwa include, in wt. % of the cast iron, 3.15 to 3.16 wt. % carbon, 2.66-2.86 wt. % silicon, 0.65 to 1.18 wt. % copper, 0.7 to 0.78 wt. % manganese, 0.04 to 0.06 wt. % sulfur, and 0.10 to 0.12 wt. % phosphorous. U.S. Pat. No. 4,891,076 and U.S. Pat. No. 5,985,052 also disclose example cast iron compositions.
One type of cast iron is referred to as gray cast iron, or gray iron. There are various grades of gray iron, and a typical gray iron composition includes, in weight percent (wt. %) of the gray iron, 2.0 to 4.0 wt. % carbon, 1.25 to 3.25 wt. % silicon, 0.75 to 1.25 wt. % manganese, 0.08 to 0.12 wt. % sulfur, and 0.07 to 0.2 wt. % phosphorous, based on the total weight of the gray iron.
Recently, there has been increased demand for piston rings including complex physical features, such as advanced oil groove designs, to provide increased performance and reduce costs. However, the cast irons of the prior art are oftentimes difficult to machine, or require expensive alloying additions to achieve the desired physical properties, which limits their use in piston rings of internal combustion engine applications.